The papers in Volume 29 of Tax Policy and the Economy illustrate the depth and breadth of the taxation-related research by NBER research associates, both in terms of methodological approach and in terms of topics. In the first paper, former NBER President Martin Feldstein estimates how much revenue the federal government could raise by limiting tax expenditures in various ways, such as capping deductions and exclusions. The second paper, by George Bulman and Caroline Hoxby, makes use of a substantial expansion in the availability of education tax credits in 2009 to study whether tax credits have a significant causal effect on college attendance and related outcomes. In the third paper, Casey Mulligan discusses how the Affordable Care Act (ACA) introduces or expands taxes on income and on full-time employment. In the fourth paper, Bradley Heim, Ithai Lurie, and Kosali Simon focus on the "e;young adult"e; provision of the ACA that allows young adults to be covered by their parents' insurance policies. They find no meaningful effects of this provision on labor market outcomes. The fifth paper, by Louis Kaplow, identifies some of the key conceptual challenges to analyzing social insurance policies, such as Social Security, in a context where shortsighted individuals fail to save adequately for their retirement.